The present invention relates to a storage system and its data restoration method, and, for instance, is suitably employed in technology for performing the backup of a storage sub system having a function of dynamically allocating a data area of a volume storing data, and restoring such backup data.
Conventionally, a storage sub system having a function of dynamically allocating a data area of a volume storing data is known, and various types of technologies relating to such storage sub system have been proposed.
For example, Japanese Patent Laid-Open Publication No. 2005-11316 discloses a storage system having a storage sub system, and a switch device for dynamically allocating a data area in the storage sub system to a virtual volume. In this case, when a write request from a host computer is received in the switch device with this storage system, upon receiving such write request from the host computer, the storage sub system dynamically allocates a data area to the virtual volume, and updates a mapping table recording the correspondence of the virtual volume and the data area in the storage sub system allocated to such virtual volume.
Further, with this storage system, the mapping table is updated in the switch device, allocation of the data area no longer used by the host computer among the data areas allocated to the virtual volume is released, and further the mapping table is further updated.
Meanwhile, Japanese Patent Laid-Open Publication No. 2003-122509 discloses a storage system having a remote copy function of restoring the storage sub system by replicating (backing up) data by transferring it to a remote storage sub system, and returning the backup data in the event of a disaster such as the loss of data in the storage sub system. In this case, the storage system transfers data synchronously or asynchronously with the remote storage sub system, and manages the progress thereof.
Further, with this storage system, when backing up data and storing it for a long period of time, data of all areas of the storage sub system is stored in a tape library of a tape device managed by a server installed for controlling such backup.
Nevertheless, when combining the foregoing function of dynamically allocating the data area and the remote copy function, upon restoring the backup data, it becomes necessary to write data in all areas of a virtual volume in the storage sub system of the restoration destination.
In particular, when the storage sub system of the backup destination is a tape device or an old model and does not possess the function of dynamically allocating a data area, upon performing backup, information concerning the allocated data area will be lost, and, in connection with this, upon performing restoration, an unnecessary data area will be allocated to the virtual volume of the storage sub system. Thus, a problem will arise in that the data area is wastefully consumed, and, as a result, the data area of the storage sub system cannot be used efficiently.